U.S. Pat. No. 4,688,388, assigned to the assignee hereof, discloses apparatus for service and recharge of refrigeration equipment, with particular application to automotive air conditioning equipment. A vacuum pump and a refrigerant charge container are housed within a wheel-mounted cabinet and configured for selective connection, by electrically operated solenoid valves and hoses carried by the cabinet, to refrigeration equipment under service. The refrigerant container is carried by a scale that provides electrical output signals as a function of weight of refrigerant remaining in the container. A microprocessor-based controller receives the scale signals and control signals from an operator panel for automatically cycling through vacuum and refrigerant charge stages in a programmed mode of operation. The microprocessor-based controller includes an alphanumeric keypad for operator programming of vacuum time and refrigerant charge quantities, an alphanumeric digital display for indicating vacuum time and charge quantities, and facility for self- or operator-implemented diagnostics. Operating conditions and stages are displayed to the operator.
U.S. Pat. No. 4,768,347, also assigned to the assignee hereof, discloses a refrigerant recovery system that includes a compressor having an input coupled through an evaporator and through a solenoid valve to the refrigeration equipment from which refrigerant is to be withdrawn, and an output coupled through a condenser to a refrigerant storage container or tank. The evaporator and condenser are contained within a closed cylindrical canister for heat exchange and oil separation, the canister having an oil drain in the bottom. The refrigerant storage container is carried by a scale having a limit switch coupled to the control electronics to prevent or terminate further refrigerant recovery when the container is full. The scale comprises a platform pivotally mounted by a hinge pin to a wheeled cart that also carries the evaporator/condenser unit, the compressor, control electronics, and associated valves and hoses.
U.S. application Ser. No. 157,579, filed Feb. 19, 1988 and assigned to the assignee hereof, now U.S. Pat. No. 4,805,416 discloses systems for recovering, purifying and recharging refrigerant in which, during a purification cycle, refrigerant is circulated from the refrigerant storage container in a closed path through a circulation valve and a filter for removing water and other contaminants, and then returned to the container. U.S. application Ser. No. 263,887 filed Oct. 28, 1988 now U.S. Pat. No. 4,878,356 and also assigned to the assignee hereof, discloses a refrigerant recovery system that includes a refrigerant storage container, refrigeration circuitry for withdrawing refrigerant from equipment to be serviced and feeding such refrigerant to the container for storage, and a scale supporting the container for sensing impending overfill of the container. The scale includes a beam horizontally rigidly cantilevered from a base. A switch is positioned adjacent to the cantilever-remote end of the beam, and is responsive to deflection of the beam to indicate impending overfill of the container and prevent or terminate operation of the refrigerant recovery system.
The refrigerant recovery and/or charging systems disclosed in the above-noted patents and applications are primarily designed and intended for use as integral or complete service systems in the environment of service stations of substantial size, and have enjoyed substantial commercial acceptance and success in such environments. However, there remains a need in the art for a simple and economical electronic scale that may be employed by service operators who already have substantial recovery and recharging equipment, who do not wish to purchase redundant equipment, and yet who desire to have automated refrigerant transfer in terms for programming and automatic-operation capability. There is also a need in the art for a compact, economical and easily portable electronic scale that may be readily transported by a refrigeration service technician to a job site, and may be employed by the technician with little advance training, for recovering refrigerant from the equipment under service and/or recharging the equipment with fresh refrigerant. It is a object of the present invention to provide an electronic refrigerant transfer scale that satisfies these needs.